Double acting pilot valve

Abstract

A pilot valve adapted for connection between a double acting fluid actuator (12) of the piston-type and a hydraulic fluid supply (21). The pilot valve comprises an elongate body (30) with an axial bore (32, 33) therethrough and a piston chamber (38) at one end of the valve body. A valve plunger (49) affixed to the piston (50) in the piston chamber (38) is mounted in the axial bore for movement between first and second operating positions in response to the selective application of pneumatic pressure to the piston (50). The valve (20) is provided with valve ports (56, 60) for accommodating connections with a hydraulic fluid reservoir (21), and a piston-type actuator (12), respectively, whereby in the first operative position of the valve plunger (49), the valve (20) is conditioned for the transmission of hydraulic fluid to a first side of the actuator piston (17) and the removal to the sump (22) of hydraulic fluid from the other second side of the actuator piston (17) through valve ports (81, 75). In the second operative of the valve plunger (49), the valve is conditioned for the transmission of hydraulic fluid to the second side of the actuator piston (17) through the valve ports (83, 81) and the removal of hydraulic fluid from the first side of the actuator piston (17) to the sump through valve ports (81, 75). In the first operative position, internal passage means (57, 58, 59) in the plunger establish communication between the reservoir (21) and the first side of the actuator piston for transmission of fluid thereto and second internal passage means (77, 78, 79) establish communication between the second side of the actuator and the sump.

What is claimed is: 
     
       1. A pilot valve adapted for connection between a hydraulic fluid supply and a double acting fluid actuator of the hydraulic piston type, said pilot valve comprising: a generally cylindrical valve body having an axial bore extending therethrough and a piston chamber housing affixed to one end of said valve body in fluid communication with the axial bore;   a valve plunger element slidably mounted in said axial bore for movement between first and second operating positions;   a piston disposed in said piston chamber housing and affixed to one end of the valve plunger element;   spring means for urging the piston and valve plunger element in a direction outwardly of said axial bore, said piston chamber housing being provided with a fluid inlet port means whereby pressurized pneumatic fluid delivered to the piston chamber through the fluid inlet port means will urge the piston and attached valve plunger element against the biasing force of said spring means to said first operating position, said valve plunger element being moved by the spring means to said second operating position when pressurized pneumatic fluid is removed from the piston chamber;   a first inlet port formed in said valve body and adapted for connection to a hydraulic fluid supply for receiving hydraulic fluid;   a first outlet port adapted for connection to a conduit for delivering hydraulic fluid to a first side of the piston in the actuator, said valve plunger element being provided with first internal passage means which in the first operating position of the valve plunger element establishes fluid communication between said first inlet port and said first outlet port for the transmission of hydraulic fluid therethrough;   first seal means located in said axial bore at a location intermediate the first inlet port and the first outlet port for sealing off communication therebetween when the valve plunger element is disposed in the second operating position;   a first bleed port formed in said valve body and adaptable for connection to a conduit communicating with a sump;   second seal means carried on said valve plunger element and positionable between the first outlet port and the first bleed port when the valve plunger element is in its first operating position for sealing off communication therebetween, said second seal means being carried by said valve plunger element to a position where it is inoperative when the valve plunger element is moved to said second operating position;   a second inlet port formed in said valve body and adapted for connection with the hydraulic fluid supply;   a second oulet port formed in said valve body adapted for connection to a conduit for delivering hydraulic fluid to the second side of the piston in said actuator;   third seal means provided on the valve plunger element and positionable between the second inlet port and said second oulet port for sealing off communication therebetween when the valve plunger element is in its first operating position;   a second bleed port formed in said valve body adapted for connection to a conduit communicating with the hydraulic sump, said valve plunger element being provided with second internal passage means which in the first operating position of the valve plunger element establishes fluid communication between the second outlet port and the second bleed port; and   fourth seal means located in said axial bore between said second outlet port and the second bleed port for sealing off communication therebetween when the valve plunger element is in the second operative position.